KR100740742B1 - Ferroelectric film, ferroelectric memory device, piezoelectric device, semiconductor device, piezoelectric actuator, liquid injection head, and printer - Google Patents

Abstract

It is a ferroelectric film formed from an oxide represented by the general formula of AB _{1 - x} Nb _x O ₃ . The element A consists of at least Pb, and the element B consists of at least one of Zr, Ti, V, W, Hf and Ta. In addition, this ferroelectric film contains Nb in the range of 0.05 ≦ x <1. This ferroelectric film can be used in any of 1T1C, 2T2C and simple matrix ferroelectric memories.

Ferroelectric, stoichiometry, sol-gel solution

Description

Ferroelectric films, ferroelectric memory devices, piezoelectric devices, semiconductor devices, piezo actuators, liquid ejection heads, and printers

1 is a cross-sectional view schematically showing a ferroelectric capacitor.

2 is a diagram showing a flowchart for forming a PZTN film by spin coating;

3 shows the P (polarization) -V (voltage) hysteresis curve of a ferroelectric capacitor.

4A to 4C are diagrams showing the surface morphology of the PZTN film in Example 1. FIG.

5A to 5C are views showing the crystallinity of the PZTN film in Example 1. FIG.

6A to 6C are diagrams showing the relationship between the film thickness and the surface morphology of the PZTN film in Example 1. FIG.

7A to 7C are diagrams showing the relationship between the film thickness and the crystallinity of the PZTN film in Example 1. FIG.

8A to 8C are diagrams showing the film thickness and hysteresis characteristics of the PZTN film in Example 1. FIG.

9A to 9C are diagrams showing the film thickness and hysteresis characteristics of the PZTN film in Example 1. FIG.

10A and 10B show leakage current characteristics of the PZTN film in Example 1. FIGS.

FIG. 11A is a diagram showing the fatigue characteristics of the PZTN film in Example 1, and FIG. 11B is a diagram showing the static imprint characteristics of the PZTN film in Example 1. FIG.

Fig. 12 is a diagram showing the structure of a ferroelectric capacitor having a SiO ₂ protective film formed by ozone TEOS in Example 1;

Fig. 13 is a diagram showing the hysteresis characteristics of the ferroelectric capacitor after forming a SiO ₂ protective film by ozone TEOS in Example 1;

FIG. 14 shows leakage current characteristics of a conventional PZT film in Example 1. FIG.

FIG. 15 is a diagram showing fatigue characteristics of a ferroelectric capacitor using a conventional PZT film in Example 1. FIG.

FIG. 16 shows the static imprint characteristics of a ferroelectric capacitor using a conventional PZT film in Example 1. FIG.

17A and 17B are diagrams showing hysteresis characteristics of the PZTN film in Example 2. FIG.

18A and 18B show the hysteresis characteristics of the PZTN film in Example 2. FIG.

19A and 19B are diagrams showing hysteresis characteristics of the PZTN film in Example 2. FIG.

20 is a diagram showing an X-ray diffraction pattern of a PZTN film in Example 2. FIG.

FIG. 21 is a diagram showing a relationship between a Pb defect amount and a composition ratio of Nb in a PZTN crystal in Example 2. FIG.

Fig. 22 is a view for explaining the crystal structure of WO ₃ which is a perovskite crystal.

23A to 23C are cross-sectional views schematically showing a step of forming a PZTN film in Example 3. FIG.

24A and 24B are views for explaining changes in lattice constants of the PZTN film in Example 3. FIG.

FIG. 25 is a view for explaining a change in lattice mismatch rate between a PZTN film and a Pt metal film in Example 3; FIG.

Fig. 26 is a diagram showing a flow for forming a conventional PZT film in a reference example by spin coating;

27A to 27E illustrate surface morphologies of PZT films in Reference Examples.

28A to 28E are views showing the crystallinity of the PZT film in the reference example.

29A and 29B show hysteresis of a tetragonal PZT film in a reference example.

30 is a diagram showing hysteresis of a conventional tetragonal PZT film in a reference example.

31A and 31B show the degassing analysis results of a tetragonal PZT film in Reference Example.

32A to 32C are views showing a manufacturing process of the ferroelectric capacitor.

33A and 33B are diagrams showing hysteresis characteristics of ferroelectric capacitors.

34 shows electrical characteristics of a ferroelectric capacitor.

FIG. 35A is a plan view schematically showing a simple matrix ferroelectric memory device, and FIG. 35B is a sectional view schematically showing a simple matrix ferroelectric memory device.

36 is a cross-sectional view showing an example of a ferroelectric memory device in which a memory cell array is integrated on a same substrate together with a peripheral circuit.

FIG. 37A is a sectional view schematically showing a 1T1C type ferroelectric memory, and FIG. 37B is an equivalent circuit diagram schematically showing a 1T1C type ferroelectric memory. FIG.

38A to 38C are views showing a manufacturing process of the ferroelectric memory.

39 is an exploded perspective view of the recording head.

40A is a plan view of the recording head, and FIG. 40B is a sectional view of the recording head.

41 is a cross-sectional view schematically illustrating the layer structure of a piezoelectric element.

42 is a schematic diagram showing an example of an ink jet recording apparatus.

FIG. 43A is a diagram showing hysteresis characteristics of the ferroelectric film with Ta added to PZT, and FIG. 43B is a diagram showing hysteresis characteristics of the ferroelectric film with W added to PZT.

Fig. 44 is a diagram showing various characteristics regarding the bonding of constituent elements of the PZT ferroelectric.

45C is a figure for demonstrating the Schottky defect of a Brown Millerite type crystal structure.

46 is a diagram for explaining space charge polarization of ferroelectrics.

The present invention relates to a ferroelectric film, a ferroelectric capacitor, a ferroelectric memory, a piezoelectric element, a semiconductor element, a method of manufacturing a ferroelectric film, and a method of manufacturing a ferroelectric capacitor.

In recent years, research and development of ferroelectric films such as PZT and SBT, ferroelectric capacitors and ferroelectric memory devices using the same have been actively conducted. The structure of the ferroelectric memory device can be roughly divided into 1T type, 1T1C type, 2T2C type, and simple matrix type. Among them, the 1T type has a short maintenance (data retention) of one month because the internal electric field is generated in the capacitor due to the structure, and the 10-year warranty generally required for semiconductors is impossible. The 1T1C and 2T2C types have almost the same configuration as the DRAM and have a selection transistor, so that the DRAM manufacturing technology can be utilized. In addition, since 1T1C type and 2T2C type have the same writing speed as SRAM, small-capacity products of 256 kbit or less have been commercialized.

Until now, mainly as a ferroelectric material, Pb (Zr, Ti) O ₃ (PZT) has been used. In the case of PZT, a mixed region of rhombohedral and tetragonal crystals such as Zr / Ti ratio of 52/48 or 40/60 and the like and its composition are used. In the case of PZT, elements such as La, Sr, and Ca may be doped and used. This area is used in order to secure the reliability most necessary for the memory element. In the hysteresis shape, the tetragonal region containing Ti in the latch is good, but a Schottky defect due to the ionic crystal structure occurs. For this reason, the leakage current characteristic or the imprint characteristic (the so-called degree of distortion of hysteresis) is generated, and it is difficult to ensure reliability.

On the other hand, the simple matrix type has a smaller cell size than the 1T1C type and the 2T2C type, and the capacitor can be multilayered, so that high integration and low cost are expected.

A conventional simple matrix ferroelectric memory device is disclosed in Japanese Patent Laid-Open No. 9-116107 and the like. The same publication discloses a driving method for applying a voltage equal to 1/3 of a write voltage to an unselected memory cell when writing data to a memory cell.

However, this technique does not specifically describe the hysteresis loop of the ferroelectric capacitor required for operation. In order to obtain a simple matrix ferroelectric memory device that can actually operate, a hysteresis loop having good angular formation is essential. As a ferroelectric material that can cope with this, a tetragonal PZT having a large number of Ti is considered as a candidate, but as in the 1T1C and 2T2C type ferroelectric memories described above, securing reliability is the most important problem.

In addition, PZT tetragonal crystals exhibit hysteresis characteristics having a squareness suitable for memory applications, but they are not practical because they lack reliability. The reason is as follows.

First, the PZT tetragonal thin film after crystallization tends to have a higher leakage current density as the Ti content is higher. In addition, when a so-called static imprint test is performed in which data is written only once in either the + or − direction, and heated and maintained at 100 ° C., the data is read out, almost no data is left after 24 h. These are intrinsic to Pb and Ti, which are constituent elements of PZT and PZT, which are ionic crystals, and this is the biggest problem of PZT tetragonal thin films composed of Pb and Ti. This problem is large because PZT perovskite is an ionic crystal, which is intrinsic to PZT.

Fig. 44 is a list of the main energies involved in the bonding of the respective constituent elements of PZT. It is known that PZT contains many oxygen voids after crystallization. That is, in FIG. 44, Pb-O has the smallest binding energy among the PZT constituent elements, and it is expected that the Pb-O will simply break upon firing heating or polarization inversion. In other words, when Pb is released, O is released on the basis of charge neutrality.

Next, at the time of heat holding, such as an imprint test, each constituent element of PZT vibrates and repeats collision, but Ti is the lightest in PZT constituent element, and it is easy to disengage by the vibration collision at high temperature holding | maintenance. Therefore, when Ti escapes, O leaves by the principle of charge neutrality. In addition, since the maximum valence of Pb: +2 and Ti: +4 contributes to the bonding, charge neutrality is not established except that O is released. That is, PZT easily escapes two anions called O with respect to one cation such as Pb, Ti, and the like, so that a so-called Schottky defect is easily formed.

Here, the mechanism of generation of leakage current due to oxygen vacancies in the PZT crystal will be described. FIG A~ C of Fig. 45 to 45 are views for explaining the generation of the leak current in the mirror brown oxide crystal having a light-type crystal structure represented by the general formula ABO _{2 .5.} As shown in FIG. 45A, the Brown Millerite crystal structure is a crystal structure having an oxygen deficiency with respect to the perovskite crystal structure of the PZT crystal and the like represented by the general formula ABO ₃ . And, as shown in FIG. 45B, in the Brown Millerite crystal structure, since oxygen ions come near the cation, the cation defect is hardly a cause of an increase in leakage current. However, as shown in FIG. 45C, the oxygen ions are connected in series to the entire PZT crystal, and as the oxygen deficiency increases, when the crystal structure becomes the Brown Millerite crystal structure, the leakage current increases accordingly. will be.

In addition to the occurrence of the leakage current described above, the defects of Pb and Ti and the accompanying O defects are so-called lattice defects, which cause space charge polarization as shown in FIG. 46. As a result, the PZT crystal generates an inverted system due to lattice defects due to an electric field caused by polarization of the ferroelectric, resulting in a state in which a so-called bias potential is applied, and as a result, hysteresis shifts or decreases. In addition, this phenomenon occurs quickly as the temperature increases.

The above is an intrinsic problem of PZT, and it is considered difficult to solve the above problems in pure PZT. Until now, it is impossible to realize that the memory device using tetragonal PZT has sufficient characteristics.

In the ferroelectric memory, the crystal state of the ferroelectric film included in the ferroelectric capacitor is one of the factors that determine the characteristics of the device. In the manufacturing process of the ferroelectric memory, a process of forming an interlayer insulating film or a protective film and generating a large amount of hydrogen is used. At this time, since the ferroelectric film is mainly formed from an oxide, the oxide is reduced by hydrogen generated during the manufacturing process, which may adversely affect the characteristics of the ferroelectric capacitor.

For this reason, in the conventional ferroelectric memory, in order to prevent the deterioration of the characteristics of the ferroelectric capacitor, the reduction resistance of the capacitor was ensured by covering the ferroelectric capacitor with a barrier film such as an aluminum oxide film or an aluminum nitride film. However, these barrier films require an excessive occupied area for high integration of the ferroelectric memory, and also in terms of productivity, a method of manufacturing the ferroelectric memory by a simpler process is expected.

It is an object of the present invention to provide 1T1C, 2T2C and simple matrix ferroelectric memories, including ferroelectric capacitors having hysteresis characteristics that can be used in any of 1T1C, 2T2C and simple matrix ferroelectric memories. Another object of the present invention is to provide a ferroelectric film suitable for the ferroelectric memory and a method of manufacturing the same. Another object of the present invention is to provide a piezoelectric element and a semiconductor element using the ferroelectric film. Another object of the present invention is to provide a ferroelectric capacitor, a method for manufacturing the same, and a ferroelectric memory using a ferroelectric capacitor, which can secure sufficient characteristics in a simple process requiring no barrier film.

The ferroelectric film according to the present invention is represented by the general formula of AB _{1 - x} Nb _x O ₃ , the A element is composed of at least Pb, and the B element is a combination of at least one of Zr, Ti, V, W, Hf and Ta. And Nb in the range of 0.05 ≦ x <1.

(1) The ferroelectric film according to the present embodiment is represented by the general formula of AB _{1 - x} Nb _x O ₃ , wherein the A element is composed of at least Pb, and the B element is Zr, Ti, V, W, Hf and Ta, It consists of at least one, and contains Nb in the range of 0.05 ≦ x <1.

In addition, the A element may be composed of Pb _{1 -y} Ln _y (0 < _y ≦ 0.2). And, Ln may be made of at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

(2) The ferroelectric film according to the present embodiment is represented by the general formula of (Pb _{1 - y} A _y ) (B _{1- x} Nb _x ) O ₃ , and the A element is La, Ce, Pr, Nd, Pm, Sm, Consisting of at least one of Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and the B element consists of one or more of Zr, Ti, V, W, Hf and Ta, and 0.05≤x < Nb is included in the range of 1 (more preferably, 0.1 ≦ x ≦ 0.3).

(3) The ferroelectric film according to the present embodiment has a PZT in which Ti content is higher than Zr composition, and 2.5 mol% or more and 40 mol% or less (more preferably, 10 mol% or more and 30 mol% or less) are substituted with Nb in the Ti composition. System ferroelectric film. In addition, the PZT-based ferroelectric film may have a crystal structure of at least one of tetragonal and rhombohedral systems. In addition, the PZT-based ferroelectric film may contain Si or Si and Ge of 0.5 mol% or more (more preferably, 0.5 mol% or more and less than 5 mol%). In addition, this PZT-based ferroelectric film can be formed using a sol-gel solution.

(4) The ferroelectric film according to the present embodiment is a PZT-based ferroelectric film represented by the general formula of ABO ₃ , containing Pb as a constituent element of A site and at least Zr and Ti as constituent element of B site. In this PZT-based ferroelectric film, the amount of Pb defects at the A-site is 20 mol% or less, at most with respect to the stoichiometric composition of the ABO ₃ . This ferroelectric film can contain Nb in the B site at a composition ratio equivalent to twice the amount of Pb defects in the A site. This ferroelectric film may have a Ti composition at the B site higher than the Zr composition and may have a crystal structure of a rhombohedral system. In addition, this ferroelectric film can be formed using a sol-gel solution.

5, a ferroelectric film manufacturing method according to this embodiment is a method for manufacturing PZT-family ferroelectric film, as the sol-gel solution is used a mixture a PbZrO ₃ sol-gel solution, a PbTiO ₃ sol-gel solution, and a PbNbO ₃ sol-gel solution for for .

In the method for producing a ferroelectric film according to the present embodiment, a mixture of a sol-gel solution for PbSiO ₃ may be used as the sol-gel solution.

(6) The method for producing a ferroelectric film according to the present embodiment is a method for producing a PZT-based ferroelectric film, in which Pb is included in the range of 0.9 to 1.2 when the stoichiometric composition of Pb, which is a constituent element of A site, is set to 1. It is formed using a sol-gel solution.

(7) The method for producing a ferroelectric film according to the present embodiment may include forming the PZT-based ferroelectric film on a metal film made of a platinum-based metal.

(8) In the method of manufacturing the ferroelectric film according to the present embodiment, the platinum-based metal may be at least one of Pt and Ir.

(9) A ferroelectric memory according to the present embodiment includes a first electrode which is electrically connected to either of a source or drain electrode of a CM0S transistor formed on a Si wafer, a ferroelectric film formed on the first electrode, and a ferroelectric film formed on the ferroelectric film. A capacitor comprising two electrodes, wherein the capacitor constituted by the first electrode, the ferroelectric film, and the second electrode performs a selection operation by a CM0S transistor previously formed on a Si wafer, wherein the ferroelectric film has a Ti ratio of 50. It is made of tetragonal PZT of not less than%, and 5 mol% or more and 40 mol% or less in the Ti composition is substituted with Nb, and at the same time, it is made of a ferroelectric film containing 1 mol% or more of Si and Ge.

(10) The ferroelectric memory according to the present embodiment includes a first electrode prepared in advance, a second electrode arranged in a direction crossing the first electrode, and at least an intersection region of the first electrode and the second electrode. A ferroelectric memory including a ferroelectric layer disposed and capacitors formed by the first electrode, the ferroelectric layer, and the second electrode in a matrix form, wherein the ferroelectric layer is formed of tetragonal PZT having a Ti ratio of 50% or more; , 5 mol% or more and 40 mol% or less in the Ti composition is substituted with Nb, and at the same time, a ferroelectric film containing 1 mol% or more of Si and Ge.

11, the manufacturing method of the ferroelectric memory according to this embodiment, the first raw material solution of PbZrO ₃ to form a sol-gel solution and the second raw material solution, PbTiO ₃ forming a sol-gel solution and the third raw material solution in the PbNbO ₃ sol-gel solution for forming for And crystallizing the sol-gel solution for forming PbSiO _3, which is a fourth raw material solution, after coating, wherein the first, second, and third raw material solutions are raw material liquids for forming a ferroelectric layer. It is a raw material liquid for producing the phase dielectric layer which has the catalytic effect which is indispensable in order to form a 1st, 2nd, and 3rd raw material solution as a ferroelectric layer.

(12) A method of manufacturing a ferroelectric capacitor according to the present embodiment includes forming a lower electrode on a desired gas, and a ferroelectric composed of a PZTN composite oxide containing Pb, Zr, Ti, and Nb as constituent elements on the lower electrode. After forming a film, forming an upper electrode on the ferroelectric film, forming a protective film to cover the lower electrode, the ferroelectric film, and the upper electrode, and forming at least the protective film, crystallizing the PZTN composite oxide It includes performing a heat treatment for.

According to the present embodiment, crystallization of such PZTN composite oxide is performed after formation of the protective film using a PZTN composite oxide containing Pb, Zr, Ti, and Nb as constituent elements as a material of the ferroelectric film. For this reason, even if the ferroelectric film was damaged by hydrogen generated during the process at the time of forming the protective film, the PZTN composite oxide is crystallized while recovering such damage by performing heat treatment for crystallization thereafter. Therefore, as in the related art, the formation process of the barrier film for protecting the ferroelectric film from the reduction reaction can be omitted, so that the productivity can be improved and the production cost can be reduced.

(13) In the method of manufacturing a ferroelectric capacitor according to the present embodiment, the ferroelectric film is in an amorphous state until a temporary heat treatment is performed under an oxidizing atmosphere at the time of formation, and a heat treatment for crystallizing the PZTN composite oxide is performed. It may be.

According to this embodiment, the ferroelectric film is in an amorphous state until crystallized. For this reason, in the ferroelectric film of this embodiment, the amorphous state can be prevented until formation of the protective film, thereby preventing deterioration of crystal quality due to grain boundary diffusion. In the ferroelectric film in the amorphous state, oxygen is introduced into the film because the heat treatment is performed under an oxidizing atmosphere. For this reason, in the heat treatment for crystallization, the PZTN composite oxide can be crystallized without depending on the kind of gas contained in the atmosphere.

(14) In the method for manufacturing the ferroelectric capacitor according to the present embodiment, the protective film may be formed using trimethylsilane as a silicon oxide film.

According to this embodiment, a protective film made of a silicon oxide film is formed by using trimethylsilane (TMS), which has a small amount of hydrogen generated during the process, compared to tetramethyl orthosilicate (TEOS), which is generally used for forming a silicon oxide film. Therefore, damage due to the reduction reaction to the ferroelectric film can be reduced.

(15) In the method for producing a ferroelectric capacitor according to the present embodiment, heat treatment for crystallizing the PZTN composite oxide can be performed in a non-oxidizing atmosphere.

According to this aspect, since the heat treatment for crystallization is performed in a non-oxidizing atmosphere, even if a peripheral member (for example, metal wiring) or the like other than a capacitor is included in the device during the process, for example, It is possible to prevent the oxidative damage caused by the high temperature heat treatment.

(16) The ferroelectric capacitor of this embodiment is formed using the above-described method for producing a ferroelectric capacitor.

(17) In addition, the ferroelectric film and the ferroelectric capacitor of the present embodiment can be applied to ferroelectric memories, piezoelectric elements, and semiconductor elements using the same.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment suitable for this invention is described in detail, referring drawings.

1. Ferroelectric Film, Ferroelectric Capacitor, and Method of Manufacturing the Same

1 is a cross-sectional view schematically showing a ferroelectric capacitor 100 using a ferroelectric film 101 according to an embodiment of the present invention.

As shown in FIG. 1, the ferroelectric capacitor 100 includes a ferroelectric film 101, a first electrode 102, and a second electrode 103.

The first electrode 102 and the second electrode 103 are made of a single material of a noble metal such as Pt, Ir, Ru, or a composite material mainly composed of the noble metal. When the elements of the ferroelectric are diffused into the first electrode 102 and the second electrode 103, composition deviation occurs at the interface portion between the electrode and the ferroelectric film 101, so that the angular formation of the hysteresis decreases. And the second electrode 103 are required to have a compactness in which elements of the ferroelectric are not diffused. In order to increase the compactness of the first electrode 102 and the second electrode 103, for example, a method of sputter film deposition with a heavy gas, or a method such as dispersing oxides such as Y and La in the noble metal electrode is employed. .

The ferroelectric film 101 is formed using a PZT-based ferroelectric made of an oxide containing Pb, Zr and Ti as constituent elements. In particular, in the present embodiment, the ferroelectric film 101 is characterized by employing Pb (Zr, Ti, Nb) O ₃ (PZTN) doped with Nb at the Ti site.

Nb is almost the same size as Ti (the ion radius is close and the atomic radius is the same), is twice the weight, and it is difficult for atoms to escape from the lattice even by collision between atoms by lattice vibration. In addition, the valence of Nb is +5, and horizontal stability, for example, even if Pb is leaving, the valence of Pb can be compensated for by Nb ^{5 +} release. In addition, even when Pb release | occurrence | production is carried out at the time of crystallization, it is easier for Nb with a small size to enter rather than escape | release large O.

Further, since there go valence of Nb is +4, it is possible to perform well in place of Ti ^{+ 4.} In addition, in reality, Nb is very covalently bonded, and Pb is considered to be difficult to escape (H. Miyazawa, E. Natori, S. Miyashita; Jpn. J. Appl. Phys. 39 (2000) 5679).

Until now, Nb doping with PZT has been mainly performed in a rhombohedral crystal region with a lot of Zr, but the amount is 0.2 to 0.025 mol% (J. Am. Ceram. Soc, 84 (2001) 902; Phys. Rev. Let, 83. (1999) 1347), in very small quantities. Thus, it is thought that the factor which could not dope a large amount of Nb was due to the crystallization temperature rising to 800 degreeC or more, for example, when 10 mol% of Nb is added.

Therefore, when forming the ferroelectric film 101, it is preferable to further add PbSiO ₃ silicate at a rate of, for example, 1 to 5 mol%. Thereby, crystallization energy of PZTN can be reduced. That is, when PZTN is used as the material of the ferroelectric film 101, the crystallization temperature of PZTN can be reduced by adding PbSiO ₃ silicate together with Nb addition.

Next, an example of the film-forming method of the PZTN ferroelectric film 101 applied to the ferroelectric capacitor 100 of this embodiment is demonstrated.

The PZTN ferroelectric film 101 prepares a mixed solution composed of first to third raw material solutions containing at least one of Pb, Zr, Ti, and Nb, and crystallizes oxides contained in these mixed solutions by heat treatment or the like. You can get it.

The solution was dissolved in an anhydrous state in a solvent such as first raw material solution, PZTN ferroelectric phase (相) of the constituent metal elements of, Pb and Zr by a PbZrO ₃ perovskite n- in which a condensation polymer for forming a crystal-butanol It can be illustrated.

It is possible to illustrate a solution obtained by dissolving in an anhydrous state in a solvent such as 2 raw material solution, of the PZTN ferroelectric on the constituent metal elements, Pb and Ti by PbTiO ₃ perovskite n- in which a condensation polymer for forming a crystal-butanol .

It is possible to illustrate a solution obtained by dissolving in an anhydrous state in a solvent such as a third raw material solution, as, on the configuration of the PZTN ferroelectric metal elements, Pb and Nb by PbNbO ₃ perovskite crystal in which a condensation polymer for forming a D- butanol .

When the ferroelectric film 101 made of, for example, PbZr _0.2 Ti _0.6 Nb _0.2 O ₃ (PZTN) is formed using the first, second and third raw material solutions, (first raw material solution): 2 raw material solutions): (third raw material solution) = 2: 6: 2 can be mixed. However, even if it is going to crystallize this mixed solution as it is, in order to manufacture the PZTN ferroelectric film 101, high crystallization temperature is required. In other words, when Nb is mixed, the crystallization temperature rises rapidly, and crystallization is impossible in the deviceable temperature range of 700 ° C. or lower. Therefore, 5 mol% or more of Nb is not used as a substitution element of Ti. Did not escape the stage. In addition, there was no example in the PZT tetragonal crystal in which Ti is contained more than Zr. This is clarified by reference J. Am. Ceram. Soc, 84 (2001) 902, Phys. Rev. Let, 83 (1999) 1347, and the like.

Therefore, in the present embodiment, the above-mentioned problems, as a fourth raw material solution, a solution of a condensation polymer for forming a PbSiO ₃ crystal in an anhydrous state in a solvent such as n- butanol, for example, less than 5mol% more than 1mol% This can be solved by further adding in the mixed solution.

That is, the crystallization temperature of PZTN can be crystallized in the elementable temperature range of 700 degrees C or less by using the mixed solution of the said 1st, 2nd, 3rd, and 4th solution.

Specifically, the ferroelectric film 101 is formed in accordance with the flowchart shown in FIG. A series of processes of the mixed solution coating step (step ST11), the alcohol removal step, the dry heat treatment step, and the degreasing heat treatment step (step ST12, step ST13) are performed as many times as desired, followed by firing by crystallization annealing (step ST14). The film 101 is formed.

Examples of the conditions in each step are shown below.

First, a lower electrode is formed by coating a noble metal for an electrode such as Pt on a Si substrate (step ST10). Next, the mixed liquid is applied by a coating method such as spin coating (step ST11). Specifically, the mixed solution is added dropwise onto the Pt coated substrate. After the spinning solution is spun at about 500 rpm for the purpose of spreading the dropped solution over the entire surface of the substrate, the rotating speed is lowered to 50 rpm or less and rotated for 10 seconds. The dry heat treatment step is performed at 150 ° C to 180 ° C (step ST13). Dry heat treatment is performed using a hot plate or the like in an atmospheric atmosphere. Similarly, in a degreasing heat treatment process, it carries out in air | atmosphere on the hotplate maintained at 300 degreeC-350 degreeC (step ST13). Firing for crystallization is performed using thermal rapid annealing (RTA) or the like in an oxygen atmosphere (step ST14).

Moreover, the film thickness after sintering can be about 100-200 nm. Next, after the upper electrode is formed by a sputtering method or the like (step ST15), post annealing is carried out as in the case of firing for the purpose of forming an interface between the second electrode and the ferroelectric thin film and improving the crystallinity of the ferroelectric thin film. In an atmosphere using RTA or the like (step ST16), the ferroelectric capacitor 100 is obtained.

Hereinafter, the influence on the hysteresis characteristics of the ferroelectric capacitor 100 by using the PZTN ferroelectric film 101 will be considered.

3 is a diagram schematically illustrating a P (polarization)-V (voltage) hysteresis curve of the ferroelectric capacitor 100. First, when voltage + Vs is applied, polarization amount P (+ Vs) is obtained, and when voltage is zero, polarization amount Pr is obtained. In addition, when the voltage is -1/3 Vs, the polarization amount is P (-1 / 3Vs). When the voltage is -Vs, the polarization amount is P (-Vs), and when the voltage O is again, the polarization amount -Pr. When the voltage is + 1/3 Vs, the polarization amount is P (+1/3 Vs), and when the voltage is + Vs again, the polarization amount returns to P (+ Vs) again.

In addition, the ferroelectric capacitor 100 has the following characteristics in hysteresis characteristics. First, when the voltage Vs is applied to make the polarization amount P (+ Vs), and then a voltage of -1/3 Vs is applied and the applied voltage is set to 0, the hysteresis loop is shown by the arrow A in FIG. Go to and the polarization amount has a stable value PO (0). When the voltage -Vs is applied to make the polarization amount P (-Vs), and then a voltage of + 1 / 3Vs is applied and the applied voltage is 0, the hysteresis loop is indicated by arrow B in FIG. In search of the trajectory, the polarization amount has a stable value PO (1). If the difference between the polarization amount PO (0) and the polarization amount PO (1) is sufficiently obtained, it is possible to operate the simple matrix ferroelectric memory device by the driving method disclosed in Japanese Patent Laid-Open No. 9-116107 or the like.

In addition, according to the ferroelectric capacitor 100 of the present embodiment, the crystallization temperature can be lowered, the hysteresis angle improvement and the Pr can be improved. In addition, the improvement in the angular formation of hysteresis by the ferroelectric capacitor 100 has a remarkable effect on the stability of interference which is important in driving a simple matrix type ferroelectric memory device. In a simple matrix ferroelectric memory device, a voltage of ± 1/3 Vs is applied to a cell that has not been written or read, so that the polarization does not change with this voltage, so-called interference characteristics need to be stabilized. In fact, the inventors of the present invention is a general PZT when the polarization is applied 10 ⁸ times in the direction of 1/3 Vs pulse to invert the polarization from a stable state polarization appears, but a decrease of about 80%, this embodiment of the ferroelectric capacitor 100 According to the present invention, it was confirmed that the reduction amount was 10% or less. Therefore, when the ferroelectric capacitor 100 of the present embodiment is applied to the ferroelectric memory device, the simple matrix memory can be put into practical use.

Below, the detailed Example about this embodiment is described.

(Example 1)

In this embodiment, PZTN according to the present invention is compared with conventional PZT. All the film-forming flow used the above-mentioned FIG.

Pb: Zr: Ti: Nb = 1: 0.2: 0.6: 0.2, 1: 0.2: 0.7: 0.1 and 1: 0.3: 0.65: 0.05. That is, Nb addition amount was made into 5-20 mol% of the whole. Here a PbSiO ₃ was added in 0-1%.

The surface morphology of the film at this time is shown in Figs. 4A to 4C. In addition, when the crystallinity of this film is measured by the X-ray diffraction method, it is as shown to FIG. 5A-5C. In the case of 0% (none) shown in Fig. 5A, only the dielectric dielectric pyroclaw was obtained even when the crystallization temperature was raised to 800 ° C. In addition, in the case of 0.5% shown in FIG. 5B, it was a mixture of PZT and a pyrochlore. Further, in the case of 1% shown in Fig. 5C, a PZT (111) single alignment film was obtained. In addition, crystallinity was also better so far as not obtained.

Next, for the 1% addition PZTN thin film of PbSiO ₃ , the film thickness was set to 120 to 200 nm, as shown in Figs. 6A to 6C and 7A to 7C, respectively. The crystallinity was proportional to the film thickness. 6A to 6C are electron micrographs showing the surface morphology at a film thickness of 120 nm to 200 nm, and C of FIG. 7A to 7 at a film thickness of 120 nm to 200 nm. It is the measurement result by the X-ray-diffraction method which showed the crystallinity of the PZTN thin film. Further, as shown in Figs. 8A to 8C and Figs. 9A to 9C, hysteresis characteristics with good angular formation were obtained in both the film thickness and the range of 120 nm to 200 nm. 9A to 9C are enlarged views of the hysteresis curve of A to C of FIG. 8. In particular, as shown in Figs. 9A to 9C, in the PZTN thin film of this example, it was confirmed that the hysteresis was surely open and saturated at a low voltage of 2V or less.

Also, as shown in FIG. 10A and FIG. 10B, the leakage characteristics are 5 × 10 ⁻⁸ to 7 × 10 ⁻⁹ at 2V application (at saturation) regardless of the film composition or film thickness. Very good at A / cm 2.

_{Next, PbZr 0 .2 Ti 0 .6 Nb} 0 .2 the measurement of the characteristic, and the static imprint fatigue thin bar, as shown in A and B of Figure 11 of Figure 11 and were very satisfactory. In particular, the fatigue characteristics shown in FIG. 11A are very good despite the use of Pt for the upper and lower electrodes.

In addition, as shown in FIG. 12, ozone TEOS is formed on the ferroelectric capacitor 600 on which the lower electrode 602, the PZTN ferroelectric film 603 of the present embodiment, and the upper electrode 604 are formed on the substrate 601. An attempt was made to form the SiO ₂ film 605. Conventionally, when PZT forms an SiO ₂ film by ozone TEOS, it is known that PZT crystals are broken so that hydrogen generated from TEOS passes through the upper Pt to reduce PZT and does not exhibit hysteresis completely.

However, the PZTN ferroelectric film 603 according to the present embodiment hardly deteriorated as shown in Fig. 13, and maintained good hysteresis. That is, it was found that the PZTN ferroelectric film 603 according to the present embodiment is also strong in reducing resistance. Further, in the tetragonal PZTN ferroelectric film 603 according to the present invention, when Nb does not exceed 40 mol%, good hysteresis is obtained depending on the amount of Nb added.

Next, the conventional PZT ferroelectric film was evaluated for comparison. Conventionally, PZT was Pb: Zr: Ti = 1: 0.2: 0.8, 1: 0.3: 0.7, and 1: 0.6: 0.4, respectively. As shown in Fig. 14, the leakage characteristics deteriorate as the Ti content increases. In the case of Ti: 80%, the leakage characteristics become 10 ^-5 A / cm 2 when applied at 2V, and are suitable for memory applications. I could not see. Similarly, as shown in Fig. 15, the fatigue characteristics deteriorated as the Ti content increased. In addition, it can be seen that almost no data is read after the imprint, as shown in FIG. 16.

As can be seen from the above embodiment, the PZTN ferroelectric film according to the present embodiment has not only solved the problems of leakage current increase and imprint characteristic deterioration, which are considered to be caused by the nature of PZT. The tetragonal PZT can be used for memory purposes regardless of the type and structure of the memory. In addition, for the same reason, this material is applicable to piezoelectric element applications in which tetragonal PZT is not used.

(Example 2)

In this embodiment, ferroelectric characteristics were compared by changing the amount of Nb added to 0, 5, 10, 20, 30, and 40 mol% in the PZTN ferroelectric film. 5 mol% PbSiO ₃ silicate was added to all samples. Moreover, methyl succinate was added to the sol-gel solution for ferroelectric film formation used as a raw material for film formation, and pH was set to 6. All of the film-forming flows use the above-mentioned FIG.

17 to 19 show hysteresis characteristics of the PZTN ferroelectric film of this embodiment.

As shown in Fig. 17A, when the amount of Nb added is 0, leakage hysteresis is obtained. However, as shown in Fig. 17B, when the amount of Nb added is 5 mol%, good hysteresis characteristics with high insulation are obtained. .

In addition, as shown in FIG. 18A, the ferroelectric properties were hardly changed until the amount of Nb added was 10 mol%. Even when Nb addition amount was 0, although it leaked, there was no change in ferroelectric characteristics. In addition, as shown in B of FIG. 18, when the amount of Nb added was 20 mol%, very good hysteresis characteristics were obtained.

However, as shown in Figs. 19A and 19B, when the amount of Nb added exceeds 20 mol%, it is confirmed that the hysteresis characteristics change significantly and deteriorate.

Therefore, as shown in FIG. 20 when the X-ray diffraction patterns are compared. When the amount of Nb added is 5 mol% (Zr / Ti / Nb = 20/75/5), the (111) peak position does not change when the PZT film does not conventionally contain Nb, but the amount of Nb added is 20 mol% (Zr / As the Ti / Nb was increased to 20/60/20 and 40 mol% (Zr / Ti / Nb = 20/40/40), the (111) peak shifted to the low angle side. That is, although the composition of PZT has many Ti and is a tetragonal area | region, it turns out that an actual crystal is a rhombohedral crystal. In addition, it can be seen that the ferroelectric properties change as the crystal system changes.

In addition, when 45 mol% of Nb was added, hysteresis did not open and ferroelectric properties could not be confirmed (not shown).

In addition, although the PZTN film which concerns on this invention has already demonstrated very high insulation, when the conditions for PZTN being an insulator were calculated | required here, it is as FIG.

In other words, the PZTN film according to the present invention has a very high insulating property, and this is a composition ratio corresponding to twice the amount of Pb defects, so that Nb is added to the Ti site. Also, as can be seen from the crystal structure of WO _{3 shown} in Fig. 22, the perovskite crystal is established even when A-site ions are deficient in 100%, and WO ₃ is known to be easily changed in crystal system.

Therefore, in the case of PZTN, by adding Nb, the amount of Pb deficiency is actively controlled and the crystal system is controlled.

This shows that the PZTN film of this embodiment is very effective also for application to a piezoelectric element. In general, when PZT is applied to a piezoelectric element, a rhombohedral crystal region having a high Zr composition is used. At this time, PZT having a high Zr is called soft PZT. This literally means that the crystal is smooth. For example, although soft PZT is used also for the ink ejection nozzle of an inkjet printer, since it is too soft, it cannot push out with the ink pressure because it is too high viscosity.

On the other hand, tetragonal tetragonal PZT is called hard PZT, and it means that it is hard and fragile. However, in the PZTN film of the present invention, it is possible to change the crystal system into a rhombohedral crystal while being a hard system. Further, the crystal system can be arbitrarily changed by the amount of Nb added, and since the PZT ferroelectric film containing a large amount of Ti has a small dielectric constant, the device can be driven at a low voltage.

This makes it possible to use a hard PZT, which has not been used so far, for example for an ink ejection nozzle of an inkjet printer. In addition, since Nb brings softness to PZT, it is possible to provide PZT which is moderately hard and not fragile.

Finally, as described so far, in this embodiment, not only Nb addition but also silicate addition at the same time as Nb addition, the crystallization temperature can be reduced.

(Example 3)

In this embodiment, for example, a platinum-based metal such as Pt or Ir used as an electrode material of a ferroelectric capacitor constituting a memory cell portion of a ferroelectric memory, or a piezoelectric actuator constituting an ink ejection nozzle portion of an inkjet printer, for example. The effectiveness of using a PZTN film was examined from the point of lattice matching when the PZTN film was formed on a metal film made of a metal film. The platinum-based metal is a material useful as an electrode material as a base film for determining the crystal orientation of the ferroelectric film when the PZT-based ferroelectric film is used for device application. However, since the lattice matching between the two sides is not sufficient, the fatigue characteristics of the ferroelectric film have been a problem for device applications.

Therefore, the inventors of the present invention have developed a technique for improving the lattice mismatch between the PZT-based ferroelectric film and the platinum-based metal thin film by including Nb in the constituent elements of the PZT-based ferroelectric film. The film forming step of the PZT-based ferroelectric film in this case is shown in Figs. 23A to 23C.

First, as shown in FIG. 23A, the saw | substrate 11 is prepared. As the substrate 11, one in which a TiOx layer was formed on an SOI substrate was used. Moreover, as the board | substrate 11, a suitable thing can be selected and used out of what consists of a well-known material.

Next, as shown in FIG. 23B, a metal film (first electrode) 102 made of Pt is formed on the substrate 11 by, for example, a sputtering method, and thereafter, C of FIG. As shown in the figure, a PZTN film is formed as the ferroelectric film 101 on the metal film 102. As a material for forming a PZTN film, a sol-gel solution can be used, for example. More specifically, PbZrO ₃ sol-gel solution, a sol-gel solution for PbTiO ₃ for, and a PbNbO ₃ sol-gel solution for being mixed with, and uses the addition of the sol-gel solution for PbNbO _3. In addition, since the PZTN film contains Nb in its constituent elements, the crystallization temperature is high. For this reason, in order to reduce the crystallization temperature, it is preferable to use a sol-gel solution for PbSiO ₃ further added. In this embodiment, the sol-gel mixed solution described above is applied onto the Pt metal film 102 by spin coating, and subjected to a predetermined heat treatment to crystallize. The flow of the film forming step is the same as that shown in FIG. 2.

In this embodiment, the lattice constants of the crystals were measured using the X-ray diffraction method for the PZTN film obtained by adding Nb in an amount ranging from 0 mol% to 30 mol%. same. According to FIG. 24A and FIG. 24B, as the addition amount of Nb increases, it turns out that the lattice constant in the a-axis (or b-axis) and the lattice constant in the c-axis are closer. In addition, V (abc) in A of FIG. 24 is an index which volume-converted lattice constants (a, b, c). Further, A is also of V / V ₀ of 24, a ratio of the V (abc) of the PZTN crystal of the index V ₀ by volume of the lattice constant of PZT crystals are not Nb added is converted. Thus, V (abc) or V / V ₀ Also in the column, it can be confirmed that the crystal lattice of PZTN crystals decreases as the amount of Nb added increases.

From the lattice constant of the PZTN film formed by adding Nb, the lattice mismatch rate with the lattice constants (a, b, c = 3.96) of the Pt metal film was calculated and plotted with the amount of Nb added (mol%) as the horizontal axis. 25 is shown. According to FIG. 25, the effect of the inclusion of Nb in the PZT-based ferroelectric film is not only an effect of improving the ferroelectric properties as in each of the above-described embodiments, but also the lattice constant to the lattice constant of platinum-based metal crystals such as Pt. It was confirmed that there was also a close effect. In particular, it was confirmed that the effect was remarkable in the region where the amount of Nb added was 5 mol% or more.

Therefore, using the method of the present invention, the lattice mismatch between the metal film as the electrode material and the ferroelectric film is reduced. For example, when the amount of Nb added is 30 mol%, the lattice mismatch rate is confirmed to improve to about 2%. In the crystal structure of PZTN, this results in a strong bond in which the Nb atom, which substitutes the Ti atom at the B-site, has both ionic and covalent bonds between O atoms, and the bonding force functions in the direction of compressing the crystal lattice, It is thought that the lattice constant changes in the direction of decreasing.

In addition, platinum-based metals such as Pt are chemically stable materials, and are suitable as electrode materials for ferroelectric memories and piezoelectric actuators. According to the method of the present embodiment, even when a PZTN film is directly formed on this Pt metal film, lattice mismatch is more than conventional. In addition to being relaxed, the interface properties can be improved. Therefore, the method of this embodiment can reduce fatigue deterioration of a PZT-based ferroelectric film, and can be said to be suitable for device applications such as ferroelectric memories and piezoelectric actuators.

(Reference example)

In the present example, PbZr _{0 .4} Ti _{0 .6} O ₃ ferroelectric films were manufactured.

In the conventional method, a solution containing excess Pb of about 20% is used, for the purpose of suppressing volatile Pb and reducing the crystallization temperature. However, it is unclear how the excess Pb is formed in the formed thin film, and therefore, the amount of excess Pb should be suppressed to the minimum amount of Pb inherently.

Thus, excess Pb of 0, 5, 10, 15, 20% of 10 wt% Ti PbZr _{0 .4 0 .6} O ₃ sol-gel solution for the formation of concentration by using the (n- butanol solvent), and 10% by weight PbSiO ₃ sol-gel solution for the formation of concentration: _0.4 (solvent n- butanol) to, respectively, by addition of 1mol%, by performing the respective steps of a step ST20~ step ST25 shown in Figure 26, 200㎚ of PbZr ₀ Ti _{0 .6} An O ₃ ferroelectric film was formed. The surface morphology at this time is as shown in Figs. 27A to 27C, and the XRD pattern is as shown in Figs. 28A to 28C.

Conventionally, about 20% excess Pb is required, but it is shown that crystallization fully advances with 5% excess Pb. This indicates that a slightly 1 mol% PbSiO ₃ catalyst lowered the crystallization temperature of PZT, so that excessive Pb was hardly needed. Thereafter, as a solution for forming PZT, PbTiO ₃ , and PbZrTiO ₃ , a 5% Pb excess solution was used.

Next, PbZrO ₃ sol-gel solution for the formation of 10 wt% concentration (solvent: n- butanol) and 10% PbTiO ₃ sol-gel solution for forming the weight concentration (solvent: n- butanol), a 4: the solution was mixed at a ratio of 6 10 wt% PbSiO ₃ sol-gel solution for the formation of concentration on:, 200㎚-PbZr _{0 .4} according to (the solvent n- butanol), the flow of Figure 2, using a mixture solution was added 1mol% Ti _{0 .6} O ₃ A ferroelectric film was produced. At this time, as shown in FIG. 29A and FIG. 29B, the hysteresis characteristics had good angle formation. At the same time, however, it was found to be leakage.

Furthermore, for comparison, by a conventional method, using the above-described flow of Figure 26, the 10 wt% PbZr _{0 .4} sol-gel solution for forming the Ti _{0 .6} O ₃ concentration (solvent: n- butanol) in 10 wt. % PbSiO ₃ sol-gel solution for the formation of a concentration (solvent: n- butanol) for using the mixed solution was added 1mol%, to prepare a 200㎚-PbZr _0.4 Ti _0.6 O ₃ ferroelectric thin film. At this time, as shown in Fig. 30, the hysteresis characteristics were not so good that the hysteresis was obtained.

Thus, the degassing analysis was performed using the respective ferroelectric films, as shown in FIG. 31A and FIG. 31B.

As shown in FIG. 31A, in the conventional ferroelectric film made of the PZT sol-gel solution, degassing on H or C was always observed with respect to the temperature rise from room temperature to 1000 ° C.

Meanwhile, as shown in B of FIG. 31, a sol-gel solution for forming PbZrO _{3 at} 10 wt% concentration (solvent: n-butanol) and a sol-gel solution for forming PbTiO _{3 at} 10 wt% concentration (solvent: n-butanol) In the case of the ferroelectric film according to the present invention using a solution mixed at a ratio of 4: 6, it can be seen that almost no degassing gas is observed until decomposition.

This sol-gel solution for forming PbZrO ₃ of 10 wt% density of a 4:: (n- butanol solvent) and a solution mixed at a ratio of 6 (solvent n- butanol) and 10% PbTiO ₃ sol-gel solution for the formation of a concentration by weight By use, PbTiO ₃ is first crystallized on Pt by a sol-gel solution for forming PbTiO ₃ (solvent: n-butanol) at a concentration of 10% by weight in a mixed solution, which becomes a crystal initial nucleus, and also a lattice miss of Pt and PZT. By eliminating the match, it was thought that PZT was easily crystallized. In addition, by using the mixed solution, it is considered that PbTiO ₃ and PZT are continuously formed at a good interface, and are connected by good hysteresis angulation.

2. Method of manufacturing ferroelectric capacitor

32A to 32C are cross-sectional views schematically showing examples of the manufacturing process of the ferroelectric capacitor according to the embodiment of the present invention.

(1) First, as shown in FIG. 32A, a lower electrode 102, a ferroelectric film 101, and an upper electrode 103 are sequentially formed on a desired base 110. FIG.

As the base 110, a suitable one can be arbitrarily adopted according to the use of a ferroelectric capacitor, such as a semiconductor substrate or a resin substrate, for example, and is not particularly limited.

As the lower electrode 102 and the upper electrode 103, for example, one composed of a single precious metal such as Pt, Ir, Ru, or a composite material mainly composed of the precious metal can be adopted. In addition, the lower electrode 102 and the upper electrode 103 can be formed using a well-known film-forming method, such as a sputtering method and a vapor deposition method, for example. In addition, when the constituent elements of the ferroelectric are diffused into the lower electrode 102 and the upper electrode 103, a composition shift occurs at the interface portion between the electrode and the ferroelectric film 101, so that the angular formation of the hysteresis decreases. And the upper electrode 103 are required to have a compactness such that the constituent elements of the ferroelectric do not diffuse. Therefore, in order to increase the compactness of the lower electrode 102 and the upper electrode 103, a method such as sputter film deposition with a heavy gas or dispersing oxides such as Y and La in the noble metal electrode can be adopted. .

The ferroelectric film 101 is a so-called PZTN composite oxide containing Pb, Zr, Ti, and Nb as constituent elements. The ferroelectric film 101 can be formed by applying a sol-gel solution containing Pb, Zr, Ti, and Nb onto the lower electrode 102 using, for example, a spin coating method. Examples of such sol-gel solutions include Pb and Zn in the first sol-gel solution in which the condensation polymer is dissolved in a solvent such as n-butanol in anhydrous state to form PbZrO ₃ perovskite crystals by Pb and Zr, constituent metal elements on the PZTN ferroelectric. In order to form PbTiO ₃ perovskite crystals by Ti, the second sol-gel solution in which the condensation polymer is dissolved in a solvent such as n-butanol in anhydrous state, and PbNbO ₃ pe using Pb and Nb among constituent metal elements on the PZTN ferroelectric In order to form a lobite crystal, what mixed the 3rd sol-gel solution which melt | dissolved the condensation polymer in the solvent, such as n-butanol, in anhydrous state can be used. In forming the ferroelectric film 101, in order to lower the crystallization temperature of the PZTN composite oxide, a sol-gel solution containing silicate or germanate may be added. Specifically, for example, to form PbSiO ₃ crystals, the fourth sol-gel solution in which the condensation polymer is dissolved in a solvent such as n-butanol in anhydrous state is further contained in the mixed sol-gel solution at, for example, 1 mol% or more and less than 5 mol%. Can be added. By mixing such 4th sol-gel solution, it becomes possible to crystallize the crystallization temperature of the PZTN composite oxide which Nb contains in a structural element in which crystallization temperature becomes high in the elementable temperature range of 700 degrees C or less.

In addition, the ferroelectric film 101 is subjected to a temporary heat treatment to such a coating film at a temperature (for example, 400 ° C. or lower) at which the PZTN composite oxide does not crystallize in an oxidizing atmosphere, thereby leaving the PZTN composite oxide in an amorphous state. It is preferable. As a result, since the ferroelectric film 101 is in an amorphous state, grain boundaries do not exist, and the process described later can be performed while preventing diffusion of the constituent elements. In addition, performing this temporary heat treatment in an oxidizing atmosphere also serves to introduce an oxygen component necessary for crystallizing the PZTN composite oxide into the ferroelectric film 101 after formation of a protective film which will be described later.

(2) Next,, SiO ₂ diagram, as shown in the 32 B, by etching the lower electrode 102, ferroelectric film 101, and the upper electrode 103 and processed into a desired shape, so as to cover these ( A protective film 104 made of a silicon oxide) film is formed. At this time, the protective film 104 can be formed by CVD using trimethylsilane (TMS). Since trimethylsilane (TMS) has a smaller amount of hydrogen generated during the CVD process than tetramethylorthosilicate (TEOS), which is generally used for forming silicon oxide films, when trimethylsilane (TMS) is used, a ferroelectric film ( Process damage by the reduction reaction to 101 can be reduced. In addition, since the formation process of the protective film 104 using trimethylsilane (TMS) can be performed at low temperature (room temperature-350 degreeC) compared with the formation process (forming temperature 400 degreeC or more) using TEOS, the process of (1) In the case where the ferroelectric film 101 is in an amorphous state, crystallization of the PZTN composite oxide can be prevented by heat generated in the process of forming the protective film 104 and the like, and the amorphous state can be maintained.

(3) Next, as shown in FIG. 32C, a heat treatment for crystallizing the PZTN composite oxide constituting the ferroelectric film 101 can be performed to obtain a ferroelectric capacitor having the PZTN ferroelectric crystal film 101a. . In this heat treatment, the PZTN composite oxide can be crystallized not only under an oxygen atmosphere but also under a non-oxidizing gas atmosphere such as Ar or N ₂ , or by heat treatment in the air.

Here, the SiO ₂ protective film using TMS is formed on the ferroelectric capacitor consisting of the Pt lower electrode, the PZTN ferroelectric film, and the Pt upper electrode by applying the manufacturing method of the present embodiment, and after forming the SiO ₂ protective film, the PZTN ferroelectric is formed in an oxygen atmosphere. The results of measuring the hysteresis characteristics of the capacitors in the case of crystallization by heat treatment in the atmosphere and in the air are shown in FIGS. 33A and 33B. FIG. 33A shows a case where the heat treatment is performed in an oxygen atmosphere, and FIG. 33B shows a case where the heat treatment is performed in the atmosphere. 33A and 33B, even when the heat treatment is performed in either an atmosphere of oxygen or an atmosphere, hysteresis characteristics with good angle formation are obtained despite the fact that the barrier film for hydrogen is not formed. . This is because the temporary heat treatment is performed under an oxidizing atmosphere when the ferroelectric film 101 is formed, and oxygen necessary for crystallization is introduced into the film in advance. That is, in the manufacturing method of this embodiment, crystallization of the ferroelectric can be performed without depending on the atmosphere of heat treatment. In the case where the heat treatment for crystallization is performed in a non-oxidizing gas atmosphere, oxidative damage due to high temperature heat treatment on peripheral members (for example, metal wirings) other than a capacitor is applied to the case where it is applied to a method of manufacturing a ferroelectric memory described later. You can prevent giving. In addition, since the heat treatment for crystallization of the PZTN composite oxide in such a step is less dependent on the type of gas in the atmosphere, the protective film 104 includes a contact hole for forming a metal wiring for connecting the upper electrode 103 to the outside. You may perform after forming to.

In addition, an SiO ₂ protective film using TMS is formed on a ferroelectric capacitor composed of a Pt lower electrode, a PZTN ferroelectric film, and a Pt upper electrode to which the manufacturing method of the present embodiment is applied, and after forming the SiO ₂ protective film, the PZTN ferroelectric is crystallized. the hysteresis characteristic in the case where the formation temperature of the SiO ₂ protective film to room temperature, 125 ℃, 200 ℃, and the comparative example, without forming the SiO ₂ protective film measuring the hysteresis characteristics when crystallized PZTN ferroelectric film, the residual polarization 2Pr The result of having measured the change of the value of is shown in FIG. Referring to Figure 34, to form a SiO ₂ protective film by any of the temperature in the room temperature, 125 ℃, 200 ℃ residue not visible from the polarization 2Pr change, is obtained, this value and there is no lower inferior case in which the SiO ₂ protective film Confirmed. That is, in the manufacturing method of the present embodiment, even when the ferroelectric film 101 is damaged by hydrogen generated during the process when the protective film 104 is temporarily formed, heat treatment for crystallization of the PZTN composite oxide is performed thereafter. Since the PZTN composite oxide is crystallized while recovering such damage, the formation process of the barrier film for protecting the ferroelectric film 101, which is conventionally required, from reduction reaction can be omitted, thereby improving productivity and reducing production cost. can do.

3. Ferroelectric Memory

35A and 35B show the structure of the simple matrix ferroelectric memory device 300 in the embodiment of the present invention. FIG. 35A is a plan view thereof, and FIG. 35B is a sectional view taken along the line A-A of FIG. 35A. The ferroelectric memory device 300 includes a predetermined number of word lines 301 to 303 formed on the substrate 308 and a predetermined number of bit lines as shown in FIGS. 35A and 35B. (304 to 306). Between the word lines 301 to 303 and the bit lines 304 to 306, a ferroelectric film 307 made of PZTN described in the above embodiments is inserted, so that the word lines 301 to 303 and the bit lines 304 to 306 are inserted. A ferroelectric capacitor is formed in the intersection region of.

In the ferroelectric memory device 300 in which the memory cells constituted by the simple matrix are arranged, writing and reading into the ferroelectric capacitor formed at the intersection of the word lines 301 to 303 and the bit lines 304 to 306 are performed. It is performed by a peripheral drive circuit, a read amplification circuit, etc. (these are called "peripheral circuits") not shown. This peripheral circuit may be formed by a MOS transistor on a substrate separate from the memory cell array and connected to the word lines 301 to 303 and the bit lines 304 to 306, or the substrate 308 may be a single crystal silicon substrate. It is also possible to integrate peripheral circuits on the same substrate as the memory cell array.

36 is a cross-sectional view showing an example of the ferroelectric memory device 300 in which the memory cell array in this embodiment is integrated on the same substrate together with the peripheral circuit.

In FIG. 36, a MOS transistor 402 is formed on the single crystal silicon substrate 401, and this transistor formation region becomes a peripheral circuit portion. The MOS transistor 402 is composed of a single crystal silicon substrate 401, a source / drain region 405, a gate insulating film 403, and a gate electrode 404.

The ferroelectric memory device 300 further includes an oxide film 406 for element isolation, a first interlayer insulating film 407, a first wiring layer 408, and a second interlayer insulating film 409.

In addition, the ferroelectric memory device 300 has a memory cell array made of a ferroelectric capacitor 420, and the ferroelectric memory 420 has a lower electrode (first electrode or second electrode) 410, which is a word line or a bit line. ), A ferroelectric film 411 including a ferroelectric phase and a phase dielectric, and an upper electrode (second electrode or first electrode) 412 formed on the ferroelectric film 411 to be a bit line or a word line.

The ferroelectric memory device 300 has a third interlayer insulating film 413 on the ferroelectric capacitor 420, and the memory cell array and the peripheral circuit portion are connected by the second wiring layer 414. In the ferroelectric memory device 300, a protective film 415 is formed on the third interlayer insulating film 413 and the second wiring layer 414.

According to the ferroelectric memory device 300 having the above configuration, the memory cell array and the peripheral circuit portion can be integrated on the same substrate. The ferroelectric memory device 300 shown in FIG. 36 has a configuration in which a memory cell array is formed on a peripheral circuit portion. However, the memory cell array is not disposed on the peripheral circuit portion, and the memory cell array is in planar contact with the peripheral circuit portion. It is good also as a structure.

Since the ferroelectric capacitor 420 used in this embodiment is comprised from the PZTN which concerns on the said embodiment, the angular formation of hysteresis is very good and it has a stable interference characteristic. In addition, since the ferroelectric capacitor 420 has less damage to peripheral circuits and other elements due to the lowering of the process temperature, and less damage to the process or other elements, in particular, the ferroelectric capacitor 420 suppresses deterioration of hysteresis due to damage. can do. Therefore, by using the ferroelectric capacitor 420, the simple matrix ferroelectric memory device 300 can be put to practical use.

37A shows a structural diagram of a 1T1C type ferroelectric memory device 500 as a modification. 37B is an equivalent circuit diagram of the ferroelectric memory device 500.

As shown in A of FIG. 37, the ferroelectric memory device 500 includes a lower electrode 501, an upper electrode 502 connected to a plate line, and a ferroelectric film 503 to which the PZTN ferroelectric of the present embodiment is applied. A switching transistor element 507 (1T) having a capacitor 504 (1C) and one of the source / drain electrodes connected to the data line 505 and a gate electrode 506 connected to the word line. It is a memory device having a structure very similar to DRAM. Since the 1T1C type memory can be written and read at a high speed of 100 ms or less, and the written data is nonvolatile, it is promising for replacement of the SRAM.

4. Method of manufacturing ferroelectric memory

Hereinafter, the case where the manufacturing method described in the section "2. Manufacturing method of ferroelectric capacitor" is applied to the manufacturing method of the ferroelectric memory will be described.

38A to 38C are cross-sectional views schematically showing one example of the manufacturing process of the ferroelectric memory according to the embodiment of the present invention.

In the present embodiment, first, as shown in FIG. 38A, the lower electrode 102, the PZTN ferroelectric film 101, and the upper electrode 103 of the ferroelectric capacitor 100 are sequentially formed on the base 110. . At this time, the PZTN ferroelectric film 101 is subjected to a temporary heat treatment in an oxidizing atmosphere and is in an amorphous state. As the base 110, for example, as shown in FIG. 38A, one in which the cell selection transistor 116 is formed on the semiconductor substrate 111 can be used. The transistor 116 may have a source / drain 113, a gate oxide film 114, and a gate electrode 115. In addition, a plug electrode 117 made of, for example, tungsten or the like is formed on one source / drain 113 of the transistor 116 so as to be connected to the lower electrode 102 of the ferroelectric capacitor 100. A stack structure can be adopted. In the substrate 110, the transistor 116 is separated from cell to cell by the element isolation region 112, and the interlayer insulating film 118 formed of, for example, an oxide film on the transistor 116. Can have

Next, in the manufacturing process of this embodiment, as shown in FIG. 38B, the ferroelectric capacitor 100 is patterned to desired size and shape. Subsequently, an SiO ₂ protective film 104 is formed using trimethylsilane (TMS) to cover the ferroelectric capacitor 100, and after forming a contact hole 105 for external connection therein, heat treatment is performed to form the PZTN ferroelectric. Crystallization is performed to form the PZTN ferroelectric film 101a. In crystallization of PZTN ferroelectric, heat treatment for crystallization can be performed in a non-oxidizing atmosphere. In this manner, oxidative damage due to high temperature heat treatment can be prevented for peripheral members (for example, metal wirings) and the like other than the ferroelectric capacitor 100.

Finally, as shown in FIG. 38C, a ferroelectric is formed in the SiO ₂ protective film 104 by forming contact holes for connecting the transistor 116 to the outside, and forming metal wiring layers 191 and 192. Get memory. According to the manufacturing process of this embodiment, the formation process of the barrier film for protecting the ferroelectric film 101 which was conventionally required from a reduction reaction can be skipped, and productivity can be improved and production cost can be reduced. Further, even if such a barrier film forming process is omitted, the ferroelectric capacitor 100 having hysteresis characteristics having good angular formation can be formed, so that a ferroelectric memory having excellent characteristics can be obtained.

In addition, although the manufacturing process of the so-called 1T1C-type ferroelectric memory has been described above, the manufacturing method of the ferroelectric capacitor of the present embodiment is, in addition, various cell systems such as so-called 2T2C type and simple matrix type (cross point type). It can also be applied to the manufacturing process of ferroelectric memory using.

5. Piezoelectric element and ink jet recording head

The ink jet recording head in the embodiment of the present invention will be described in detail below.

An ink jet recording in which a part of the pressure generating chamber communicating with the nozzle opening for discharging ink droplets is constituted by a diaphragm, and the diaphragm is deformed by a piezoelectric element to pressurize the ink in the pressure generating chamber to discharge the ink droplets from the nozzle opening. Two types of heads are utilized, one using a piezoelectric actuator in a longitudinal vibration mode that extends and contracts in the axial direction of the piezoelectric element, and one using a piezoelectric actuator in a bending vibration mode.

In the case of using the actuator of the bending vibration mode, for example, a uniform piezoelectric layer is formed by a film forming technique over the entire surface of the vibration plate, and the piezoelectric layer is cut into a shape corresponding to the pressure generating chamber by the lithography method. It is known that a piezoelectric element is formed so as to be independent of each pressure generating chamber.

39 is an exploded perspective view showing an outline of an ink jet recording head according to one embodiment of the present invention, FIGS. 40A and 40B are plan views and AA 'cross-sectional views of FIG. 39, and FIG. 41 is a piezoelectric element. A schematic diagram showing a layer structure of 700 is shown. As shown, the flow path forming substrate 10 is made of a silicon single crystal substrate in the surface orientation 110 in this embodiment, and on one surface thereof, made of silicon dioxide previously formed by thermal oxidation. An elastic membrane 50 having a thickness is formed. In the flow path formation substrate 10, a plurality of pressure generating chambers 12 are arranged in the width direction thereof. Moreover, the communication part 13 is formed in the area | region of the longitudinal direction outer side of the pressure generation chamber 12 of the flow path formation board 10, and the communication part 13 and each pressure generation chamber 12 are each pressure generation chamber. It communicates with the ink supply path 14 provided in every 12. Moreover, the communication part 13 communicates with the reservoir part 32 of the sealing board | substrate 30 mentioned later, and comprises a part of the reservoir 800 used as a common ink chamber of each pressure generation chamber 12. As shown in FIG. The ink supply passage 14 is formed to have a width narrower than that of the pressure generating chamber 12, and maintains a constant flow path resistance of the ink flowing into the pressure generating chamber 12 from the communicating portion 13.

In addition, the nozzle plate 20 in which the nozzle opening 21 which communicates in the vicinity of the edge part on the opposite side to the ink supply path 14 of each pressure generation chamber 12 in the opening surface side of the flow path formation board | substrate 12 is an adhesive agent, It adhere | attaches through the heat welding film.

On the other hand, as described above, an elastic film 50 having a thickness of, for example, about 1.0 μm is formed on the side opposite to the opening surface of the flow path forming substrate 10, and the thickness is formed on the elastic film 50. For example, an insulator film 55 of about 0.4 mu m is formed. Further, on the insulator film 55, the lower electrode film 60 whose thickness is, for example, about 0.2 µm, the piezoelectric layer 70 whose thickness is, for example, about 1.0 µm, and the thickness are, for example, For example, the upper electrode film 80 having a thickness of about 0.05 μm is laminated in a process described later to constitute the piezoelectric element 700. Here, the piezoelectric element 700 refers to a portion including the lower electrode film 60, the piezoelectric layer 70, and the upper electrode film 80. In general, one electrode of the piezoelectric element 700 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure generating chamber 12. In this case, a portion composed of one of the patterned electrodes and the piezoelectric layer 70, in which piezoelectric distortion occurs by the application of voltage to both electrodes, is referred to as a piezoelectric active portion. In the present embodiment, the lower electrode film 60 is used as the common electrode of the piezoelectric element 700, and the upper electrode film 80 is used as the individual electrode of the piezoelectric element 700. There is no harm in reverse. In either case, the piezoelectric active part is formed in each pressure generating chamber. In addition, here, the piezoelectric element 700 and the diaphragm which a displacement generate | occur | produces by the drive of the said piezoelectric element 700 are collectively called a piezoelectric actuator. The piezoelectric layer 70 is provided independently for each pressure generating chamber 12, and is composed of a plurality of layers of ferroelectric films 71 (71a to 71f) as shown in FIG.

The ink jet recording head constitutes a part of the recording head unit including an ink flow path communicating with an ink cartridge or the like, and is mounted on the ink jet recording apparatus. 42 is a schematic diagram showing an example of the ink jet recording apparatus. As shown in Fig. 42, in the recording head units 1A and 1B having the ink jet recording head, the cartridges 2A and 2B constituting the ink supply means are detachably provided, and this recording head unit 1A is provided. , 1B on which the carriage 3 is mounted, is provided on the carriage shaft 5 attached to the apparatus main body 4 so as to be axially movable. The recording head units 1A and 1B are each for discharging the black ink composition and the color ink composition, for example. Then, the driving force of the drive motor 6 is transmitted to the carriage 3 via a plurality of gears and timing belts 7 (not shown), whereby the carriage 3 on which the recording head units 1A and 1B are mounted has a carriage shaft. It moves along (5). On the other hand, a platen 8 is provided along the carriage shaft 5 in the apparatus main body 4, and a recording sheet S which is a recording medium such as paper fed by a paper roller or the like not shown is placed on the platen 8. It is supposed to be conveyed.

Moreover, although the ink jet recording head which discharges ink as a liquid jet head was demonstrated as an example, this invention is the object of the liquid jet head and the whole liquid jet apparatus which used the piezoelectric element. As the liquid jet head, for example, a recording head used in an image recording apparatus such as a printer, a color material jet head used in the production of color filters such as a liquid crystal display, an organic EL display, and an electrode for FED (surface light emitting display) The electrode material injection head used, the bioorganic material injection head used for biochip manufacture, etc. are mentioned, for example.

Since the piezoelectric element of this embodiment uses the PZTN film according to the above embodiment for the piezoelectric layer, the following effects are obtained.

(1) Since the covalent bond in the piezoelectric layer is improved, the piezoelectric constant can be improved.

(2) Since the deficiency of PbO in the piezoelectric layer can be suppressed, the occurrence of abnormality at the interface with the electrode of the piezoelectric layer is suppressed and the electric field is easily added, and the efficiency as a piezoelectric element can be improved.

(3) Since the leakage current of the piezoelectric layer is suppressed, the piezoelectric layer can be thinned.

In addition, since the liquid jet head and the liquid jet device of the present embodiment use the piezoelectric element including the piezoelectric layer described above, the following effects are particularly obtained.

(4) Fatigue deterioration of the piezoelectric layer can be reduced, so that the change over time of the displacement amount of the piezoelectric layer can be suppressed and the reliability can be improved.

As mentioned above, although embodiment suitable for this invention was described, this invention is not limited to the above-mentioned, It can implement by various modified aspects within the range of the summary of this invention.

For example, the ferroelectric film 101 has an equivalent effect even if Ta, W, V, and Mo are added as an additive material instead of Nb with respect to PZT. Moreover, even if Mn is used as an addition material, it has an effect according to Nb. In the same manner, in order to prevent Pb detachment, it is also conceivable to substitute Pb with elements of +3 or more valence, and as candidates thereof, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb. And lanthanides such as Dy, Ho, Er, Tm, Yb, and Lu. In addition, germanium salt (Ge) other than silicate (Si) can be used as an additive which promotes crystallization. FIG. 43A shows the hysteresis characteristics when 10 mol% of Ta is used as the additive material instead of Nb with respect to PZT. 43B shows the hysteresis characteristics when 10 mol% of W is used as the additive material instead of Nb with respect to PZT. Even when Ta is used, it turns out that the effect equivalent to Nb addition is acquired. Moreover, also when W is used, it turns out that there exists an effect equivalent to Nb addition in that the hysteresis characteristic with favorable insulation is obtained.

According to the present invention, it is possible to provide 1T1C, 2T2C and simple matrix ferroelectric memories, including ferroelectric capacitors having hysteresis characteristics that can be used in any of 1T1C, 2T2C and simple matrix ferroelectric memories. According to the present invention, a ferroelectric film suitable for the ferroelectric memory, a piezoelectric element and a semiconductor element using the ferroelectric film, a piezoelectric actuator, a liquid jet head, and a printer can be provided. According to the present invention, it is possible to provide a ferroelectric capacitor, a method of manufacturing the same, and a ferroelectric memory using a ferroelectric capacitor, which can secure sufficient characteristics in a simple process requiring no barrier film.

Claims (10)

Represented _by the general formula of AB _1-x Nb _x O ₃ , A element consists of Pb _1-y Ln _y , B element contains Zr and Ti, Ti composition in element B is higher than Zr composition, 0.05 ≦ x <1, Ln is made of at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, A ferroelectric film with 0 <y ≤ 0.2. Represented _by the general formula of (Pb _1-y A _y ) (B _1-x Nb _x ) O ₃ , A element is made of at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, B element contains Zr and Ti, Ti composition in element B is higher than Zr composition, A ferroelectric film with 0.05 ≦ x <1. The method according to claim 1 or 2, The B element further includes at least one of V, W, Hf, and Ta. The method according to claim 1 or 2, A ferroelectric film with 0.1 ≦ x ≦ 0.3. Substrate, A lower electrode formed on the substrate; A ferroelectric film according to claim 1 or 2 formed on the lower electrode; An upper electrode formed on the ferroelectric film; Peripheral circuit electrically connected to the lower electrode and the upper electrode Ferroelectric memory device comprising a. Substrate, A lower electrode formed on the substrate; A ferroelectric film according to claim 1 or 2 formed on the lower electrode; An upper electrode formed on the ferroelectric film; Peripheral circuit electrically connected to the lower electrode and the upper electrode Semiconductor device comprising a. A lower electrode, A ferroelectric film according to claim 1 or 2 formed on the lower electrode; An upper electrode formed on the ferroelectric film Piezoelectric element comprising a. With diaphragm, The piezoelectric element according to claim 7 formed on the diaphragm. Piezoelectric actuator comprising a. Substrate, A piezoelectric actuator according to claim 8 formed on the substrate; A flow path formed in the substrate, A nozzle plate formed under the substrate and having a nozzle opening in communication with the flow path Liquid injection head comprising a. A recording head unit having a liquid ejecting head according to claim 9, A carriage on which the recording head unit is mounted; Drive unit for moving the carriage Printer comprising a.

Images